1. Field of the Invention
The present invention relates to a fluid control valve to be used in a semiconductor manufacturing device, in particular, relates to a chemical fluid control valve including a resin valve main body.
2. Related Art
For instance, as shown in FIG. 22, a chemical fluid control valve 200 to be used in a semiconductor manufacturing device includes: a resin valve main body 210 including a valve chamber 215 providing communication between an inlet port 211 and an outlet port 212 formed in opposite side surfaces via a valve seat 261, the valve chamber 215 opening at the center of an upper surface, and the valve seat 261 provided in an inner wall 216 defining the valve chamber 215; a diaphragm valve element 241 configured to come into or out of contact with the valve seat 261; and a valve upper body 220 having a drive section for driving the diaphragm valve element 241. The main body 210 is formed with an inflow passage 213 formed like an L shape extending through the inner wall 216 to communicate the inlet port 211 with the valve chamber 215. In manufacture of such a main body 210 by injection molding, when a resin flow is branched in two or more directions and, after flowing by a certain distance, the branched flows merge again. In this merging area, weld lines are apt to occur. Weld lines occur when molten resin solidifies before completely fuses. Thus, the area where weld lines occur may lack sufficient mechanical strength and cause fluid leakage.
In the resin valve main body 210, accordingly, in the case where weld lines occur in the valve seat 261 with which the diaphragm valve element 241 comes into or out of contact, a seal portion 217 that seals a retainer portion of the valve element 241, and others, the valve main body 210 after molding is conventionally subjected to cutting, grinding, and others to remove the weld lines.
However, the cutting and others after molding are not preferable due to cost increase and also have a problem that burrs and dust generated in the cutting are left in the valve and may become particles in a semiconductor manufacturing process.
To solve the above problems, for example, Patent Documents 1 to 3 disclose techniques to avoid the weld lines without using cutting or the like.
Patent Document 1 discloses a method for molding resin components by making resin flows merge in a cavity while keeping a molten state. In this method, a cavity mold is arranged to be removable from a mold main unit so that the cavity mold is heated and cooled in a short time. Accordingly, the cavity mold can be heated and cooled in a short time. This configuration can prevent the generation of weld lines without using extra energy.
Patent Document 2 discloses a valve seat processing method in which a flat contact surface of a heated heating member is pressed against a valve seat serving as a seal surface of a resin valve, thereby melting the valve seat, and then the contact surface of the heating member is separated from the valve seat. According to this processing method, the seal surface of the valve seat is melted and made flat along the contact surface of the heating member, thus removing molding defects such as weld lines.
Patent Document 3 discloses a method for manufacturing a cylindrical part by supplying molten resin to fill a runner annularly formed along the outside of a part forming section, and the molten resin filled in the runner is made to flow into the part forming section from the outer periphery side thereof. In this manufacturing method, the molten resin is supplied to uniformly flow from the runner to the outside of the part forming section, and thus the molten resin flows radially inwardly from outside to inside of the part forming section. Accordingly, the part forming section does not have an area where the molten resin branched into two flow directions join together. Thus, no weld lines occur.